Vapor phase conversion of cyclohexanecarboxylic acid to cyclohexanone

ABSTRACT

A process for preparing cyclohexanone whereby a mixture of cyclohexane carboxylic acid in the vapor phase and a gas containing molecular oxygen at temperatures of from about 250*C. to 600*C. are passed through a static catalyst bed, said catalyst containing copper or a copper salt.

United States Patent Murray et a1.

[ 51 Aug. 22, 1972 [54] VAPOR PHASE CONVERSION OF CYCLOHEXANECARBOXYLIC ACID TO CYCLOHEXANONE Inventors: Edward J. Murray, Buffalo; Leon 0. Winstrom, East Aurora, both of N.Y.

Allied Chemical Corporation, New York, N.Y.

Filed; Jan. 17, 1969 Appl. No.: 800,795

Related US. Application Data Continuation of Ser. No. 615,843, Feb. 13, 1967, abandoned, which is a continuation of Ser. No. 360,132, April 15, 1964, abandoned.

Assignee:

US. Cl. ..260/586 R, 252/475 Int. Cl ..C07c 45/18 Field of Search ..260/5 86 R; 252/475 References Cited UNITED STATES PATENTS 3,219,689 11/1965 Bigot et a]. ..260/586 R X FOREIGN PATENTS OR APPLICATIONS 1,296,938 5/1962 France ..260/586 R 299,947 8/1965 Netherlands ..260/586 R 6,504,809 10/1965 Netherlands ..260/586 R OTHER PUBLICATIONS Bigot et al., Rec. Trav. Chim Vol. 83, pp. 1,199 1,210 (1964) Primary ExaminerBemard Helfin Assistant ExaminerNorman Morgenstern Attorney-Michael S. .larosz [57] ABSTRACT 7 Claims, No Drawings VAPOR PHASE CONVERSION OF CYCLOHEXANECARBOXYLIC ACID T CYCLOHEXANONE This application is a continuation of our application I presence of steam which is mixed with the vapor charge before the latter enters the converter.

Our process yields 60 percent or more of crude filed Febl 1967, now abandoned, 5 product based on the weight of cyclohexanecarboxylic which was a continuation of our application Ser. No. id i d, Th r de product contains up to about 360,132, filed P 1964 now abandoned 45 percent by weight cyclohexanone as well as minor P mventlol} relates to the P P of amounts (about 3 percent or less) of cyclohexanol and f kfa'tones from ahFychc carboxyllc aclds- In B cyclohexene, and unreacted cyclohexane-carboxylic concerned Y t vapor-Phase convetson acid. The unreacted cyclohex'anecarboxylic acid may of cyclohexanecarboxyhc acid to cyclohexanone. be separated out by steam distillation and recycled cycloilexangne Is a valuable mtermed'ate m the back to the converter, which also contains unreacted plodulmon of caprolaqmn a precursor of comer starting material. In this manner an efficient continuous clally important synthetic fibers. Process is afforded It Is an object of the present Invention to dev'se a The present invention is illustrated by the following procedure for the vapor phase converslon of cyclohexexamples in which parts are by weight unless otherwise aneqarboxyhc aclfi to cyclohexanone noted and temperatures are'in degrees centigrade.

It is another ob ect of the present invention to devise PL S l 4 a procedure'that will be inexpensive, employing readily to available reagents and conventionally designed equip- In Examples 1 to 4, the results of which are presented ment. in Table I below, the following general procedure was This and other objects and advantages will be apused. parent from the following description of our invention. Cycl hexan arboxylic acid Was evaporated into a We have made the surprising discovery that Stream y u g g gh a dy 0f the cyclohexane-carboxylic acid is converted to cyclohexmolten atild mamtamed at 160 mixed Wlth anone by contacting a mixture of the vaporized acid Steam t Passed through a mercury coolefl refractory and a gas containing molecular oxygen with a Copper tube WhlCl'I contained a heated copper zinc catalyst catalyst at a temperature of about 250 to 600 C. This (440 also 50 Percent volds) Prep as may be done batchwise or in a continuous mannen described in U.S. Pat. No. 2,552,300, and a preheating According to a preferred embodiment of the present seem of fused alumna (Ahmdum A138 103 invention, we employ the catalyst of U.S. Pat. No. grams 0'066 323 ig l gasfes from the 1 2,552,300, which comprises copper and zinc in the g to a t l 'z form of the metals or their oxide or in part as the metals con ensef an gave a con c w w separa mm and in part asthe oxides an organic layer and an aqueous layer. The crude orla er was withdrawn dried over molecular sieves Conveniently, the present process is carried out in a y s .tabl h be ed com, net contajnin the (Lmde 4A; 1 part per 50 parts by volume crude) and u] e c am r ca a e g analyzed by vapor phase chromatography. heated catalyst and a preheating section consisting of a 40 suitable inert material such as alumina. The mixture of EXAMPLE 5 oxygen containing gas and vapors of cyclohexanecar The procedure employed in Examples l-4 was reboxyllc acld Passed through the conv'el'ter f peated except that the air and steam flow rates were the Vapors and the catalyst are brought Into bnef and varied at intervals. After each interval of operation intimate contact- All effluent heat exchange medlum, under a given set of conditions, the.crude product obe.g. refluxing mercury, surrounding the converter tained was analyzed by vapor phase chromatography. assists in the Co t ol Of h r l ing g ly exothermic The average rate of consumption of cyclohexane carreaction. Such a converter is disclosed in U.S. Pat. No. boxylic acid was 83 parts per hour. The results of this 1,604,739. experiment are tabulated in Table 2 TABLE 1 Percent cyclohexane- Parts of air Percent carboxylic per part Percent cyclo I acid in Cyclo- Minimum (1) cyclo- Parts of Initial Back yield hexanone crude hexaneflow rates hexane- Duration steam catalyst pressure of crude in crude product t x. carboxylic carboxylic of run per part tempermm. Hg product product recycled to No. acid Air Steam acid (hours) of air ature (2) (3) (4) converter 1 I46 gms/hr. 452 534 1.75 l6 0.73 403 62.4 23.9 70.1 2 134 gmS/hr. 457 594 1.9 13.5 0.81 405 70 47.9 30.8 61.1 3 85.5 gms/hr. 428 465 2.74 36.5 0.67 404 45 37.8 33.0 53.3 4 gms/hr. 387 319 2.23 18 0.51 360 72 43.5 44.19 43.79

Notes:

(I) alculated from initial catalyst temperature and expressed in liters of gas per hour.

(2) Atmospheric pressure was 750 mm. Hg.

(3) Based on weight of cyclohexanecarboxylic acid vaporized. Contains about 5% water. (4) As determined by vapor phase chromatography of dried crude product.

TAB LE 2 Percent cyclohexane- Percent carboxylic cycloacid in Maximum (1) Maximum Back hexanone crude flow rates Parts Duration catalyst pressure in crude product (4). steam per of run tempermm. Hg product recycled to perating interval Air Steam pan air (hours) ature (2) (3) (4) converter 429 345 0.5 2.5 361 64 47.57 32.94 433 232 0.33 l 360 55 31.24 57.08 509 256 0.3] l 465 50 29.82 59.04 533 0 l 500 50 30.09 55.89 538 236 0.27 l 519 63 30.63 57.59 558 0 0 1.5 567 80 23.56 46.26

Notes:

(l) Calculated from the maximum catalyst temperature and expressed in liters of gas per hour- (2) lnitial catalyst temperature was 320. (3) Atmospheric pressure was 750 mm. Hg.

(4) As determined by vapor phase chromatography of the dried crude product.

It can thus be seen that a novel vapor phase process for converting cyclohexanecarboxylic acid to cyclohexanone has been devised.

The foregoing examples illustrate the process of our invention and it will be obvious to those skilled in the art that considerable variation in the illustrative details can be made without departing from the spirit and scope of the invention.

For example, the conditions of temperature, pressure, contact time, etc., to be maintained in our process will depend upon the catalyst employed, the activity of the catalyst (as influenced, for example, by its method of preparation), the concentration of the various components of the vapor phase mixture treated and other factors familiar to those skilled in the art.

Flow rates may vary from 0.2 to parts cyclohexane carboxylic acid per hour per part of catalyst. The

reactor charge may contain from 1 to 3 parts oxygen containing gas per part of cyclohexane carboxylic acid and from 0 to 5 parts of steam per part of oxygen containing gas.

Although we prefer to employ the copper zinc catalyst disclosed in US. Pat. No. 2,552,300 (column 2, line 50), any copper-containing substance can be used including copper metal cuprous oxide copper chromite cupric oxide.

As the oxygen-containing gas, oxygen or oxygen mixed with an inert diluent such as nitrogen can be used in the present process. Preferably, however, air is employed.

To initiate the reaction, the catalyst temperature should be at least about 250C. According to the preferred embodiment of the instant invention, the catalyst temperature at the start of the reaction is about 300 to 420C. However, catalyst temperatures considerably above the initial temperature result during the reaction due to the exothermic character of the process. In order to obtain satisfactory yields of cyclohexanone, reaction conditions should be selected so as to avoid catalyst temperature in excess of about 600 C.

The present invention affords cyclohexanone, a valuable intermediate in the manufacture of caprolactam by the vapor phase conversion of cyclohexanecarboxylic acid employing inexpensive and readily available reagents and equipment of conventional design.

We claim:

1. The continuous process of producing cyclohexanone which comprises continuously passing a mixture of vaporous cyclohexanecarboxylic acid and a gas containing molecular oxygen through a static bed of a catalyst consisting essentially of mixtures of copper, cuprous oxide or cupric oxide with zinc or zinc oxides, said catalyst being in the solid state throughout said passage, at a temperature between about 250C. and about 600C. to effect conversion of said acid to cyclohexanone, continuously discharging reaction products from said static bed and recovering cyclohexanone therefrom.

2. The process of claim 1 wherein the catalyst consists essentially of copper and zinc.

3. The continuous process of producing cyclohexanone which comprises continuously passing a mixture of vaporous cyclohexanecarboxylic acid and a gas containing molecular oxygen in a ratio of l to 3 parts of said gas to 1 part of said acid through a static bed of a catalyst consisting essentially of a mixture of copper and zinc, said catalyst being in the solid state throughout said passage, at a temperature between about 300C. to about 600C. to effect conversion of said acid to cyclohexanone, continuously discharging reaction products from said static bed and recovering cyclohexanone therefrom.

4. The process according to claim 3 wherein said gas comprises oxygen.

5. The process according to claim 3 wherein said gas comprises a mixture of oxygen and nitrogen.

6. The continuous process of producing cyclohexanone which comprises continuously passing a mixture of vaporous cyclohexanecarboxylic acid and air in a ratio of l to 3 parts of air to 1 part of said acid in the presence of up to 5 parts of steam per part by weight of air through a static bed of catalyst consisting essentially of a mixture of copper and zinc, said catalyst being in the solid state throughout said passage, at a temperature between about 250C. and about 600C. to effect conversion of said acid to cyclohexanone, continuously passa e through said tstatic bed.

discharging crude reaction products from said static 6 Process claim 6 f" the flow rate bed, recovering cyclohexanone therefrom, recovering ranges from to Parts by welght per hour of the unreacted cyclohexanecarboxylic acid from the cyclohexanecarboxyhc papa catalyst crude reaction products and recycling said acid for 5 

2. The process of claim 1 wherein the catalyst consists essentially of copper and zinc.
 3. The continuous process of producing cyclohexanone which comprises continuously passing a mixture of vaporous cyclohexanecarboxylic acid and a gas containing molecular oxygen in a ratio of 1 to 3 parts of said gas to 1 part of said acid through a static bed of a catalyst consisting essentially of a mixture of copper and zinc, said catalyst being in the solid state throughout said passage, at a temperature between about 300*C. to about 600*C. to effect conversion of said acid to cyclohexanone, continuously discharging reaction products from said static bed and recovering cyclohexanone therefrom.
 4. The process according to claim 3 wherein said gas comprises oxygen.
 5. The process according to claim 3 wherein said gas comprises a mixture of oxygen and nitrogen.
 6. The continuous process of producing cyclohexanone which comprises continuously passing a mixture of vaporous cyclohexanecarboxylic acid and air in a ratio of 1 to 3 parts of air to 1 part of said acid in the presence of up to 5 parts of steam per part by weight of air through a static bed of catalyst consisting essentially of a mixture of copper and zinc, said catalyst being in the solid state throughout said passage, at a temperature between about 250*C. and about 600*C. to effect conversion of said acid to cyclohexanone, continuously discharging crude reaction products from said static bed, recovering cyclohexanone therefrom, recovering the unreacted cyclohexanecarboxylic acid from the crude reaction products and recycling said acid for passage through said static bed.
 7. The process of claim 6 wherein the flow rate ranges from 0.2 to 10 parts by weight per hour of cyclohexanecarboxylic acid per part catalyst. 